Detented presettable tuner,particularly for uhf television



' Oct. 21, 1969 J. T. HARTEN 3,474,362

DETENTED PRESETTABLE TUNER, PARTICULARLY FOR UHF TELEVISION Filed Feb.14, 1968 2 Sheets-Sheet l ATTORNEYS 2 l a M. M N M m4 R II: a 2 on rm;IIIIQ m V T H m 1 h h m F Y w B r m W wflqjdj azg ll EEEEFW U Oct. 21,1969 J. T. HARTEN 3,474,362

DETENTED PRESETTABLE TUNER, PARTICULARLY FOR UHF TELEVISION Filed Feb.14, 1968 2 Sheets-Sheet 2 FIGS f6 SC i 22 42 a FIG? e 68 i l '[g 74 i itH! u I 1" WI! l 11 l I mm 1 l 24/ J INVENTOR 40 50/ JOHN T. HARTENATTORNEYS United States Patent O 3,474,362 DETENTED PRESETTABLE TUNER,PARTICU- LARLY FOR UHF TELEVISION John T. Harten, Longmeadow, Mass.,assignor to General Instrument Corporation, Newark, N.J., a corporationof Delaware Filed Feb. 14, 1968, Ser. No. 705,385 Int. Cl. H033 /02 US.Cl. 334-51 17 Claims ABSTRACT OF THE DISCLOSURE A detented presettabletuner of the variable capacitance type is provided, particularly for UHFtelevision. There is a fixed chassis with a rotor shaft carrying rotorplates, and a tiltable cradle carrying stator plates, the cradle beingmounted in the chassis for limited oscillation about the rotor shaft. Adetent wheel is coupled to the rotor shaft for rotation therewith, andalso a memory drum which has adjustable screw projections for finetuning or channel selection at each detented position. A linkageresponsive to and moved by the adjustable screws extends to the tiltablecradle. There is a selector shaft with r duction gearing to the rotorshaft, because the latter turns only about 180, whereas the selectorshaft turns a full revolution, and the detent wheel and the memory drumare mounted on the selector shaft rather than the rotor shaft. A hollowshaft concentric with the selector shaft is geared to the selectedadjustable screws to adjust the same. This gearing is normallydisengaged, but a slip friction clutch driven by the hollow shaft bringsthe disengaged gearing into mesh when making a channel selection. Thedetent wheel and the reduction gearing are preferably mounted at therear end of the chassis, and the memory drum and the preset mechanismincluding the slip friction clutch are conveniently mounted at theforward end of the chassis. The memory drum has sloping contour camsbetween the adjustable screws to ease the transition from one screw tothe next, and a bellows type dashpot prevents rapid oscillation of thecradle when the memory drum is rotated.

BACKGROUND OF THE INVENTION There are seventy channels in the UHF band.These are covered by continuous tuning, typically a tuner of the gangcapacitor type. However, it is desirable to provide channel selectionwith a step-by-stepor detent action as is done in the VHF band. It isnot feasible or even desirable to detent all seventy channels, becausein practice only a much smaller number of more widely spaced channelsare available in any one geographical area.

It therefore has already been suggested to subdivide the UHF band intogroups of channels, say twelve or twenty-four groups; to provide detentaction for the selection of the group; and a presettable fine tuningaction for the selection of the available channel in each group. Thismay be done by detenting the rotor shaft for the selection of thegroups, and slightly tilting the stator of the gang capacitor for theselection of the desired channel in each group. The general object ofthe present invention is to improve such a tuner.

SUMMARY OF THE INVENTION The detented presettable tuner is of thevariable capacitance type. A fixed chassis has a rotor shaft carryingrotor plates, and a tiltable cradle carrying stator plates, the cradlebeing mounted in the chassis for limited oscillation about the rotorshaft. A detent wheel is coupled to the rotor shaft for rotationtherewith. A memory drum also is coupled to the rotor shaft and hasadjustable pro- "ice jections for the fine tuning, there being oneprojection for each detented position. A linkage is provided which isresponsive to and is moved by the adjustable projections of the memorydrum, and which extends to the tiltable cradle so that the selectedprojection tilts the cradle according to the adjustment of theprojection. A selector shaft with reduction gearing turns the rotorshaft, because the latter turns only about Whereas the selector shaftmay turn a full revolution, and in preferred form both the detent wheeland the memory drum are mounted on the selector shaft rather than therotor shaft. For UHF tuning the detent wheel is for groups of channels,and the memory drum is for selection of a particular channel in thegroup.

There is also a hollow shaft concentric with the selector shaft, andgearing between the hollow shaft and that one of the adjustableprojections which is at the selected detent position. This gearing isnormally disengaged, but a slip friction clutch driven by the hollowshaft brings the disengaged gearing into mesh for tilting the cradlewhen initially making a channel selection. Thereafter there is no needto use the hollow shaft and gearing, unless it be desired to change theselected channel, or to improve the accuracy of the fine tuning.

The adjustable projections are preferably radial screws carried by thememory drum, and a gear nut is provided for each screw to adjust theamount of its radial projection from the drum. The detent wheel and thereduction gearing are mounted on the selector shaft at the rear end ofthe chassis, which shaft may be extended for connection to a motor driveif the tuner is to be remotely controlled. The memory drum and itspreset mechanism including the slip friction clutch and gearing areconveniently mounted on the selector shaft at the forward end of thechassis. The memory drum preferably has sloping contour cams between theprojecting screws, in order to ease the transition from one screw to thenext. A bellows type dashpot is connected to the cradle to prevent rapidoscillation of the cradle when the memory drum is rotated.

The foregoing and additional features are described in the followingdetailed specification, which is accompanied by drawings in which:

FIG. 1 is an elevation of a tuner embodying features of the invention;

FIG. 2 is a transverse section taken approximately on the line 22 ofFIG. 1, and includes a flexible electrical cable connection which hasbeen omitted in the other figures of the drawing;

FIG. 3 is a fragmentary view like FIG. 2, but showing the cradle tiltedtoward the right, relative to its position in FIG. 2;

FIG. 4 is an end elevation looking toward the rear of the tuner;

FIG. 5 is a bottom view of the tuner, with a part of the cradle wallbroken away to show rotor and stator plates;

FIG. 6 is a fragmentary tranverse section taken approximately on theline 6-6 of FIG. 5;

FIG. 7 shows a part of the friction clutch of the preset mechanism;

FIG. 8 is a fragmentary view drawn to enlarged scale, and explanatory ofthe adjustable screws of the memory drum; and

FIG. 9 shows a fragment of a resilient tension device for the gear nutsof FIG. 8.

Referring to the drawings, the illustrated tuner comprises a fixedchassis generally designated 12 carrying a rotor shaft 14 with rotorplates 16 (FIGS. 5 and 6). There is also a tiltable cradle 18 whichcarries stator plates 20, these being insulatedly and fixedly mounted inthe cradle 18. The parts of the tuner within the cradle 18 need not bedescribed in greater detail because they may be conventional. The cradleis capable of a limited oscillation about the axis of the rotor shaft14, as shown by the change from 'FIG. 2 to FIG. 3.

Because the rotor turns through only about one-half revolution the tunerpreferably has a selector shaft 22 which is geared to the rotor shaft 14by means of reduction gearing indicated at 24, 26. This providesapproximately a two to one ratio, so that the selector shaft 22 turnsthrough a full revolution. A detent wheel 28 is mounted on the selectorshaft 22, and a cooperating precision detent 30 bears against the detentwheel 28 for selecting the desired rotor positions accurately. In thepresent case there are twelve such positions, but a different number,say eighteen positions or twenty-four positions, may be provided.

With twelve detent positions as shown, there are six channels in eachgroup. Two detent positions, say the end two positions, would requiretuning over only five channels. The range of vernier or fine tuningadjustment, suggested by the arrow 120 in FIG. 6, is made sufficient tocover at least the six channels, and preferably covers seven or eightchannels. Overlapping is beneficial in making it possible to preset fortwo channels which are somewhat more closely spaced than anticipated andwhich fall in one group. With twenty-four detent positions, eachposition must cover at least three channels. Two positions, say the endtwo, would need to cover only two chanels. In this case the fine tuningrange is easily and preferably made to cover say five channels insteadof three, thus providing a desirable overlap at each end in all of thedetent positions.

A memory drum 32 also is mounted on the selector shaft 22 and hasadjustable projections 34 for fine tuning, there being one suchprojection for each detented position of the detent wheel. A linkage,generally designated 36, is responsive to and moved by the adjustableprojections 34 and extends to the cradle 18 so that the selectedprojection 34 tilts the cradle 18 to a fine tuning position which isdetermined by the adjustment of the projection. The memory drum 32 isaxially separated from the detent wheel 28, and has sloping contourearns 38 which ease the transition from one projection 34 to the next.

The projections 34 are adjusted by relative rotation of parts havingmating screw threads. More specifically, in this case the parts 34 arenon-rotatable radial screws carried by the memory drum, and there is agear nut 40 for each screw to adjust its radial projection from thedrum. A hollow shaft 42 is concentric with the selector 22, and operatesgearing leading to the gear nut 40 of the selected screw 34 whichcorresponds to the detent position. A part of the gear train is normallydisengaged, as will be seen in FIG. 5 by the retracted position of thegear 44, and the hollow shaft 42 turns a slip friction clutch indicatedgenerally at 46 (FIG. 5) which drives a part 48 to bring the disengagedgearing into mesh for tilting the cradle 18.

The shaft 60 normally moves to the disengaged position shown in FIG. 5,and a light spring wire 61 (FIGS. 1 and 5) may be positioned against theouter end of the shaft 60 to insure its disengagement.

Referring now to FIG. 8, the drum 32 has radial slots 50 which arenon-circular in cross section, and in which the screws 34 are disposed.In the present case the slots 50 are square in cross section, and thescrews 34 have four flats which fit in the slot 50 to prevent rotation.The gear nut 40 has gear teeth around its periphery, and is internallythreaded to mesh with the thread of the screw 34, this thread being onthe four rounded corners of the screw, and being interrupted by the fourflats. For convenience the screw may be referred to as a square screw,meaning that the shank fits non-rotatably in a square slot, and yet thescrew action is retained in relation to the gear nut 40.

The memory drum may be constructed in varied ways,

but in the present case it is made of two parts, one being a diecastdrum with the radial slots 50 (FIG. 7) open on one face, and the openface being closed by a flat circular cover plate 52. 0t its oppositeface the diecast drum is thickened enough to protect the gear nuts 40,these being received in tangentially directed slots 54. In FIG. 8 a partof the cover plate 52 has been broken away. FIGS. 2 and 3 show how theteeth of the gear nuts are exposed through tangentially directed slotsin the cover plate 52. The contour cams 38 are diecast integrally withthe drum, and extend from the outer end of one radial slot to that ofthe next radial slot.

Referring now to FIG. 5, the hollow shaft 42 turns a bevel gear 56meshing with a bevel gear 58 on shaft 60, one end of which is carried ina bearing 62, and the other end of which is carried in a horizontallyslotted bearing 64, so that shaft 60 may swing from the outer positionshown in FIG. 5, to an inner position in which gear 44 engages theadjacent gear nut 40 of the memory drum.

For this purpose the friction clutch 46 has a bent resilient washer 66or other such friction means bearing against a driven member 48.Referring to FIG. 7, the hub or driven portion of member 48 has upwardlyand downwardly projecting arms 68. Reverting to FIGS. 1 and 5, thesearms 68 rest against a fixed bracket 70 forming a part of the fixedchassis 12. It will be evident that if the shaft 60 is turned in eitherdirection its initial movement will cause either the upper or lower arm68 to bear against the bracket 70 and so by reaction to move the outerend of shaft 60 rearward, as shown by the arrow at 72 in FIG. 5, thusbringing the gear 44 into mesh with the adjacent gear nut 40 of thememory drum. Continued rotation of the hollow shaft 42 rotates the gearnut, and so alters the projection of the screw 34, thereby tilting thecradle of the tuner for channel selection in the detented group of UHFchannels.

Inasmuch as the cradle has only a limited range of oscillation, it isdesirable to protect the mechanism against abuse should the hollow shaft42 be turned forcibly when the cradle can no longer move. For thispurpose a gear in the gear train, specifically gear 44 in this case, isfrictionally driven, and for that purpose it is held between frictionaldrive members including a resilient washer shown at 45 in FIG. 5.Excessive turning of hollow shaft 42 results merely in slippage at thegear 44.

To provide friction to maintain the preset adjustment of the screw, andalso to avoid lost motion or backlash, each of the tangential slots 54(FIG. 8) is preferably provided with resilient fingers or other suchtension device 74 which bears frictionally against the gear nut 40, andwhich nearly fills the clearance space in the slot 54.

In the present case each slot receives a bifurcated spring having arms74 (FIG. 9), which straddle the screw 34 as shown in FIG. 8. These pairsof arms may be formed integrally and bent forward from an arcuate plate75, which is secured against the back face of the diecast memory drum,as by means of screws, or studs which are integral with the casting. Oneof the holes for the screws is indicated at 77 in FIG. 8. It isconvenient to subdivide the plate into say four sections, and in thepresent case each section has spring fingers to bear against three gearnuts. When the detent mechanism provides twenty-four positions, eacharcuate plate section 75 of the tension device would have six pairs ofspring fingers to take care of six gear nuts. However, I have also useda separate small back plate for each pair of spring fingers 74, on adrum with twenty-four square screws and detent positions. It will beunderstood that the tangential slots 54 which receive the gear nuts passentirely through the diecast drum, thus opening the way for reception ofthe spring fingers 74 from the rear of the drum. The screws which holdthe arcuate plates 75 against the drum have been omitted in FIGS. 1 and5.

The detent wheel 28 is made of hardened steel, and its periphery is socontoured as to minimize pressure during its movement against thedetent. The detent is of the precision type employing a hardened steelball 30 (FIG. 4) of precise size carried in a precision hole in bracket31 and moved by an upright lever 76, the lower end of which is pivotallysecured in a bracket 78, and the upper end of which is pulled toward theleft as viewed in FIG. 4, by means of a pull spring 80, the left end ofwhich is anchored on a stud 82 fixedly secured to the chassis 12. Detentmechanisms are known, but the main requirement here is for greataccuracy, in order to accurately position the rotor shaft 1-4 forreference points from which the fine tuning is accomplished.

The gear 26 is preferably of the anti-backlash type, that is, itcomprises two parts 26 and 26' (FIG. 5), one of which is fixedly securedto the rotor shaft, as by means of its hub 84, and the other of which isrotatably displaced by a pair of compression springs 86 (FIGS. 1 and 4)received in diametrically opposed slots. Such gears are well known, andare sometimes referred to as scissor gears. The arrangement eliminatesbacklash between the teeth of gear 24 and 26.

The rotor shaft 14 is carried in bearings designed for accuracy and lowtorque. There are four bearings in all, two of which mount the rotorshaft 14 in the cradle 18, and the other two of which mount the cradleassembly in the fixed chassis 12. As viewed in FIG. 5, the right or rearend of shaft 14 is carried in a ring of bearing balls 88. The chassis 12acts as the stationary part of this bearing. There is a similar ring ofbearing balls, not shown in section, but housed at 89, between the shaft14 and the cradle 18. At its forward end the shaft 14 bears against andis carried by a single ball which in turn bears against a nest of saythree balls, which are carried by a threaded stud 91 which is axiallyadjustable for thrust, and the position of which may be locked by meansof a nut 93. This ball bearing arrangement is already used in variablegang capacitors, and may be conventional except that in this case thenut 93 is formed on the outside with a cup 95 which carries a nest ofballs receiving a conical stud carried by an axially adjustable threadedplug 97, the adjustment of which may be locked by means of a lock nut94. The purpose of the bearing arrangement is to provide precisioncombined with low friction, so that channel selection may be made withminimum torque.

The linkage for tilting the cradle 18 comprises a main generally uprightlever 96 (FIG. 2), which has a hardened steel, generally cylindricalstud 98 pressed into a bushing at the lower end of the lever. This studis acted on by the screws 34 of the drum 32. The stud 9 8 is smallenough in diameter to fit between the contour cams 38 when theadjustment of the screw 34 is a relatively retracted one. The lever 96has a flanged pivot pin 102 welded thereon, and a fixed mount 100receives the pin 102, providing a long bearing pivot.

The upper end of lever 96 carries a short link 104 one end of which isbifurcated to receive the upper end of lever 96, these being joined by apivot 106. The other end of link 104 is connected by a pin 108 to thecradle 18, the connection being made rigid by an enlargement indicatedat 110 in FIG. 1. The cradle is biased in one direction by means of apull spring, best shown at 112 in FIG. 1. The lower end of this springis secured to the fixed chassis 12 as shown in FIGS. 1 and 2. The stud98 then is resiliently urged toward the adjustable screws 34. Thisspring action eliminates clearance or backlash in the linkage betweenthe memory drum 32 and the cradle 18.

The main electrical cable leading from the tuner to the rest of theapparatus (e.g. a television receiver) is shown at 114 in FIG. 2. Itextends upward, but is bent downward as shown at 116, and is held by abracket 118. The bend of the cable is so directed that it adds to theeffect of the biasing spring 112, and urges the cradle counterclockwiseas viewed in FIG. 2.

As so far described a rapid rotation of the selector shaft 22 wouldcause a rapid vibration or chattering of the mechanism, the cradle 18tending to move in and out for each step of the drum. This may beavoided by the provision of dashpot means generally designated in FIGS.1, 2 and 3. In the specific form here shown, there is an axiallycompressible rubber bellows 132 connected at one end 134 to the tiltablecradle, while the other end 136 is fixed. The end 134 may be a plasticelement which is secured to the forward end of a strap 138, which issecured to the cradle as indicated by the screws 140 in FIG. 1. The end136 may also comprise plastic elements which pass through and aresecured to the upper end of a bracket 142, the lower end of which issecured to the stationary chassis as indicated by the screw 144 in FIG.2. One end, in this case the end 136, has a constricted aperture suchthat air flows through it slowly. In consequence when the cradle istilted and compresses the bellows, the stud '98 of the linkage 36 beingin its outer position, as shown in FIG. 3, it tends to remain in thatposition, and does not move back between the successive steps of thememory drum until the drum is stopped at the selected position. Thecradle and linkage then move to proper position as determined by theadjustment of the square screw for that detented position.

If the tuner is to be used under remote control, the motor drive is mostconveniently attached to the rear end of shaft 22, which may be extendedsomewhat compared to the present showing in FIG. 1. This constitutes oneadvantage in locating the detent wheel 28 at the rear end of thechassis. Another advantage is that by locating both the reductiongearing and the detent mechanism at the rear end of the chassis, theforward end of the chassis is cleared to receive the memory drum and thepreset mechanism, as here shown.

It is believed that the construction and operation of my improveddetented presettable tuner, as well as the advantages thereof, will beunderstood from the foregoing detailed description. It will also beunderstood that while I have shown and described the tuner in apreferred form, changes may be made without departing from the scope ofthe invention.

I claim:

1. A detented presettable tuner of the variable gang capacitance type,said tuner comprising a fixed chassis, a rotor shaft carrying rotorplates, a tiltable cradle carrying stator plates, said cradle beingmounted in said chassis for limited oscillation about the axis of therotor shaft, a detent wheel rotatable with said rotor shaft, acooperating detent bearing against said detent wheel for selecting rotorpositions, a memory drum having adjustable projections for fine tuning,there being one projection for each detented position, and linkageresponsive to and moved by said adjustable projections and extending tothe tiltable cradle, whereby the selected projection tilts the cradle toa fine tuning position which is determined by the adjustment of theprojection, said memory drum being axially separated from said detentwheel and having sloping contour cams between said fine tuningprojections to ease the transition from one projection to the next.

2. A tuner as defined in claim 1, in which the rotor is designed formotion through about a half revolution, and in which there is a selectorshaft and reduction gearing between the selector shaft and the rotorshaft so that the selector shaft turns through a full revolution, and inwhich the detent wheel and the memory drum are mounted on the selectorshaft.

3. A tuner as defined in claim 2, in which the adjustable projectionsare adjusted by relative rotation of parts having mating screw threads,and in which there is a hollow shaft concentric with the selector shaft,and gearing between said hollow shaft and that one of the adjustableprojections which is at the selected detent position, and in which apart of the gearing is normally disengaged, and in which the hollowshaft turns a slip friction clutch driving a part which brings thedisengaged gearing into mesh for cradle tilt at the selected detentedposition of the tuner.

4. A tuner as defined in claim 3, in which the adjustable projectionsare radial screws carried by the memory drum, means to prevent rotationof the screws, and one of said parts comprises a gear nut for each screwto move the same to adjust its radial projection from the drum, theaforementioned gearing terminating at the Selected gear nut for rotationof the same.

5. A tuner as defined in claim 4, in which the drum has radial slotswhich are non-circular in cross section, and in which the radial screwsare disposed in said slots and said means to prevent rotation comprisesflats to prevent rotation thereof in said slots, and in which each screwis received in a corresponding gear nut which is rotatable to adjust thescrew radially of the drum, said gear nuts being received in tangentialslots to expose the gear teeth for engagement with a driving gearforming a part of the fine tuning mechanism.

6. A tuner as defined in claim 5, in which the detent wheel and thereduction gearing are mounted at the rear end of the chassis, and inwhich the memory drum and the preset mechanism including the slipfriction clutch and gearing for preset tuning are mounted at the forwardend of the chassis.

7. A tuner as defined in claim 6, in which there is slip friction meansengaging one of the gears in the gearing between the hollow shaft andthe gear nut in order to afford slippage if the hollow shaft is rotatedbeyond the limit of movement of the cradle.

8. A tuner as defined in claim 7, in which a bellows having aconstricted air passage is connected at one end to the tiltable cradlewhile the other end is fixed, in order to provide a dashpot action suchthat the cradle will not oscillate with every contour cam of the memorydrum when the said drum is rapidly rotated.

9. A detented presettable tuner of the variable gang capacitance type,said tuner comprising a fixed chassis, a rotor shaft carrying rotorplates, a tiltable cradle carrying stator plates, said cradle beingmounted in said chassis for limited oscillation about the axis of therotor shaft, a detent wheel coupled to said rotor shaft for rotationtherewith, a cooperating detent bearing against said detent wheel forselecting rotor positions, a memory drum coupled to said rotor shaft andhaving adjustable projections for fine tuning, there being oneprojection for each detented position, linkage responsive to and movedby said adjustable projections and extending to the tiltable cradle,whereby the selected projection tilts the cradle to a fine tuningposition which is determined by the adjustment of the projection, aselector shaft and reduction gearing be tween the selector shaft and therotor shaft, a hollow shaft concentric with the selector shaft, gearingbetween said hollow shaft and that one of the adjustable projectionswhich is at the selected detent position, means to cause said gearing tonormally be disengaged, and a slip friction clutch driven by said hollowshaft and moving a part which brings the disengaged gearing into meshfor cradle tilt at the selected detented position of the tuner.

10. A tuner as defined in claim 9, in which the rotor is designed formotion through 180, and in which the selec tor shaft turns a fullrevolution, and in which the detent wheel and the drum are mounted onthe selector shaft.

11. A tuner as defined in claim 9, in which the adjustable projectionsare radial screws carried by the memory drum, means to prevent rotationof the screws, and a gear nut for each screw to move the same to adjustits radial projection from the drum, the aforesaid cradle tilt shaft andgearing terminating at the selected gear nut for rotation of the same.

12. A tuner as defined in claim 11, in which the drum has radial slotswhich are non-circular in cross section, and in which the radial screwsare disposed in said slots and have flats to prevent rotation thereof insaid slots, and in which each screw is received in a gear nut which isrotatable to adjust the screw radially of the drum, said gear nuts beingreceived in tangential slots to expose the gear teeth for engagementwith a driving gear forming a part of the fine tuning mechanism.

13. A tuner as defined in claim 9, in which there is slip friction meansengaging one of the gears in the gearing between the hollow shaft andthe adjustable projection in order to afford slippage if the hollowshaft is rotated beyond the limit of movement of the cradle.

14. A tuner as defined in claim 9, in which a bellows having aconstricted air passage is connected at one end to the tiltable cradlewhile the other end is fixed to provide a dashpot action such that thecradle will not oscillate with every projection of the memory drum whenthe said drum is rapidly rotated.

15. A tuner as defined in claim 1, in which a bellows having aconstructed air passage is connected at one end to the tiltable cradlewhile the other end is fixed to pro- 'vide a dashpot action such thatthe cradle will not oscillate with every projection of the memory drumwhen the said drum is rapidly rotated.

16. A tuner as defined in claim 9, in which the detent wheel and thereduction gearing are mounted at the rear end of the chassis, and inwhich the memory drum and the preset mechanism including the slipfriction clutch and the gearing engageable with the adjustableprojections are mounted at the forward end of the chassis.

17. A tuner as defined in claim 9, in which the drum has contourprojections between the adjustable projections in order to ease thetransition from projection to projection despite differences in theradial position of the successive projections.

References Cited UNITED STATES PATENTS 6/1965 Mentzer 74-10 9/1966Leedom 7410.4l

MILTON KAUFMAN, Primary Examiner

